Low-Level Z sub(DR) Signatures in Supercell Forward Flanks: The Role of Size Sorting and Melting of Hail

The low levels of supercell forward flanks commonly exhibit distinct differential reflectivity (ZDR) signatures, including the low-ZDR hail signature and the high-ZDR arc. The ZDR arc has been previously associated with size sorting of raindrops in the presence of vertical wind shear; here this mode...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2014-01, Vol.71 (1), p.276-299
Main Authors: Dawson, D T, Mansell, E R, Jung, Y, Wicker, L J, Kimijan, M R, Xue, M
Format: Article
Language:English
Online Access:Get full text
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Summary:The low levels of supercell forward flanks commonly exhibit distinct differential reflectivity (ZDR) signatures, including the low-ZDR hail signature and the high-ZDR arc. The ZDR arc has been previously associated with size sorting of raindrops in the presence of vertical wind shear; here this model is extended to include size sorting of hail. Idealized simulations of a supercell storm observed by the Norman, Oklahoma (KOUN), polarimetric radar on 1 June 2008 are performed using a multimoment bulk microphysics scheme, in which size sorting is allowed or disallowed for hydrometeor species. Several velocitydiameter relationships for the hail fall speed are considered, as well as fixed or variable bulk densities that span the graupel-to-hail spectrum. A T-matrix-based emulator is used to derive polarimetric fields from the hydrometeor state variables.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-13-0118.1